Plasma Facing Components with Capillary Porous System and Liquid Metal Coolant Flow*

Liquid metal (LM) can create renewable protective surfaces on plasma facing components, with an additional advantage of deuterium pumping and tritium extraction if liquid lithium (LL) is used. LM can also be utilised as an efficient coolant, driven by the Lorentz force created with the help of the magnetic field in fusion devices. Capillary porous systems can serve as a conduit of LM and simultaneously provide stabilisation of the LM flow, protecting against spills into the plasma. Recently within the framework of the U.S. DoE domestic LM divertor PFC design project, we proposed a combination of a fast-flowing LM cooling system with a porous plasma facing wall (CPSF) [1]. The system takes an advantage of a magnetohydrodynamics (MHD) velocity profile, as well as attractive LM properties to promote efficient heat transfer from plasma to LL at low pumping energy cost, relative to the incident heat flux on the PFC. In case of disruption leading to excessive heat flux from plasma, LL evaporation can stabilize the temperature due to high evaporation heat and apparent vapor shielding [2]. 

The proposed CPSF was optimised analytically for conditions of a Fusion Nuclear Science Facility: 10T toroidal field and 10 MW/m² peak heat flux. Computational fluid dynamics analysis confirmed that a CPSF system with 2.5 mm square channels can pump enough LL so that no additional coolant is needed, to maintain LL PFC surface temperature below 450C, above which LL evaporation could contaminate the plasma [3]. Scaling of the flow parameters allow initial proof of concept experiments using Galinstan. Recent advances in 3D printing technologies provide new opportunities in manufacturing CPSF system components using tungsten [2], additionally SiC nano particle composites with wide variety of properties can be used.

[1] A. Khodak, R. Maingi, NME 2021

[2] P. Rindt, et al., FED 2016

[3] T. D. Rognlien and M. E. Rensink, PoP 2002